style: 给顶部导航栏添加粘性定位 (sticky top-0 z-50)，适配PC和移动端

src/components/headerBlock.tsx

@@ -38,7 +38,7 @@ const Navigation: React.FC = () => {
   }
 
   return (
-    <header className="w-full bg-white shadow-sm border-b border-gray-100">
+    <header className="w-full bg-white shadow-sm border-b border-gray-100 sticky top-0 z-50">
       <div className="max-w-full mx-auto md:px-20 sm:px-6 px-4">
         <div className="flex justify-between items-center h-18">
           {/* Logo 区域 */}